U.S. patent number 9,903,175 [Application Number 13/390,658] was granted by the patent office on 2018-02-27 for pressure control device.
The grantee listed for this patent is Nicholas Atkins, Tim Clarke, David Hare, Craig Spalding. Invention is credited to Nicholas Atkins, Tim Clarke, David Hare, Craig Spalding.
United States Patent |
9,903,175 |
Atkins , et al. |
February 27, 2018 |
Pressure control device
Abstract
A pressure control device for isolating a section of a conduit
comprises a support member, a flexible cup member mounted to the
support member, a first swellable element, the first swellable
element adapted, upon activation by an activation fluid, to urge a
first portion of the cup member outwards into engagement with a
conduit surface and at least one bypass arranged to permit the
activation fluid to bypass the swellable element and build up
behind a second portion of the cup member.
Inventors: |
Atkins; Nicholas (Bridge of
Don, GB), Spalding; Craig (Bridge of Don,
GB), Clarke; Tim (Bridge of Don, GB), Hare;
David (Bridge of Don, GB) |
Applicant: |
Name |
City |
State |
Country |
Type |
Atkins; Nicholas
Spalding; Craig
Clarke; Tim
Hare; David |
Bridge of Don
Bridge of Don
Bridge of Don
Bridge of Don |
N/A
N/A
N/A
N/A |
GB
GB
GB
GB |
|
|
Family
ID: |
41171549 |
Appl.
No.: |
13/390,658 |
Filed: |
July 29, 2010 |
PCT
Filed: |
July 29, 2010 |
PCT No.: |
PCT/GB2010/001438 |
371(c)(1),(2),(4) Date: |
May 03, 2013 |
PCT
Pub. No.: |
WO2011/020987 |
PCT
Pub. Date: |
February 24, 2011 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130263929 A1 |
Oct 10, 2013 |
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Foreign Application Priority Data
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Aug 18, 2009 [GB] |
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0914416.3 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B
33/126 (20130101); E21B 33/1208 (20130101); Y10T
137/0379 (20150401) |
Current International
Class: |
E21B
33/126 (20060101); E21B 33/12 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO2005121498 |
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Dec 2005 |
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WO |
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WO2006126925 |
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Nov 2006 |
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WO |
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WO2009074785 |
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Jun 2009 |
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WO |
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Other References
International Search Report for PCT/GB2010/001438, dated Nov. 3,
2011. cited by applicant .
International Preliminary Report on Patentability for
PCT/GB2010/001438, dated Feb. 21, 2012. cited by applicant.
|
Primary Examiner: Fuller; Robert E
Attorney, Agent or Firm: Dykas; Frank J. Dykas Law Offices,
PLLC
Claims
The invention claimed is:
1. A pressure control device for isolating a section of a conduit,
the device comprising: a support member; a flexible cup member
mounted to the support member; a first swellable element, the first
swellable element adapted, upon activation by an activation fluid,
to urge a first portion of the cup member outwards into engagement
with a surface of the conduit; at least one bypass arranged to
permit a portion of the activation fluid to bypass the swellable
element to permit build up of the portion of the activation fluid
in a void behind a second portion of the cup member to move the
second portion of the cup member into engagement with the surface
of the conduit; and at least on stiffening device adapted to
stiffen the walls of the at least one bypass and prevent activation
of the swellable element by the portion of the activation fluid
while the portion of the activation fluid is in the at least one
bypass.
2. The device of claim 1, wherein the build up of fluid behind the
second cup member portion creates a pressure on the second cup
member portion.
3. The device of claim 1, wherein the pressure control device
defines a throughbore.
4. The device of claim 3, wherein the pressure control device
further comprises a mandrel, the mandrel located in the device
throughbore.
5. The device of claim 4, wherein the at least one bypass is
defined by the first swellable element and the mandrel.
6. The device of claim 1, wherein the first cup member portion is
adapted to form a lip seal with the surface.
7. The device of claim 1, wherein the at least one bypass is
defined by the first swellable element.
8. The device of claim 1, wherein the at least one bypass is
defined by the first swellable element and the cup member first
portion.
9. The device of claim 1, wherein the pressure control device
further comprises a mandrel.
10. The device of claim 9, wherein the at least one bypass is
defined by the mandrel.
11. The device of claim 9, wherein the void is defined behind the
second cup member portion by the second cup member portion and the
mandrel.
12. The device of claim 11, wherein the void is defined behind the
second cup member portion by the second cup member portion, the
first swellable element and the mandrel.
13. The device of claim 11, wherein the void comprises at least one
inlet such that the portion of the activation fluid can flow into
the void from the at least one bypass.
14. The device of claim 11, wherein a seal is located downstream of
the void.
15. The device of claim 14, wherein the seal is an o-ring seal.
16. The device of claim 14, wherein the seal holds pressure from
one direction only.
17. The device of claim 9, wherein the support member is sealed to
the mandrel.
18. The device of claim 1, wherein the at least one stiffening
device defines a bypass either wholly or partially.
19. The device of claim 1, wherein the at least one stiffening
device defines a bypass in combination with a mandrel.
20. The device of claim 1, wherein the stiffening device is a
length of tubular.
21. The device of claim 1, wherein the at least one stiffening
device extends the full height of the first swellable element.
22. The device of claim 1, wherein the apparatus comprises at least
one anti-extrusion device.
23. The device of claim 22, wherein the at least one anti-extrusion
device defines access means to permit the fluid to access the first
swellable element.
24. The device of claim 22, wherein the at least one anti-extrusion
device is attached to a mandrel.
25. The device of claim 22, wherein the at least one anti-extrusion
device is a ring.
26. The device of claim 22, wherein the connecting member is a
tubular.
27. The device of claim 1, wherein the at least one anti-extrusion
device comprises a first anti-extrusion device preventing swelling
in a first axial direction.
28. The device of claim 27, wherein the at least one anti-extrusion
device comprises a second anti-extrusion device preventing swelling
in a second axial direction, opposite the first axial
direction.
29. The device of claim 28, wherein the first anti-extrusion device
and the second anti-extrusion device are connected.
30. The device of claim 29, wherein the first anti-extrusion device
and the second anti-extrusion device are connected by a connecting
member.
31. The device of claim 30, wherein the connecting member wholly or
partially defines the at least one bypass.
32. The device of claim 31, wherein the connecting member defines
the at least one bypass in combination with a mandrel.
33. The device of claim 1, wherein the first swellable element
comprises at least one of: ethylene propylene rubber; polyacrylic
rubber; polyethers; acrylate polymers; tetra fluoro
ethylene-propylene; and hydrogenated nitrile rubber.
34. The device of claim 1, wherein first swellable element defines
the first cup member portion.
35. The device of claim 1, wherein the first cup member portion
comprises a different material than a material of the second cup
member portion.
36. The device of claim 1, wherein the first cup member portion
comprises a swellable material.
37. The device of claim 1, wherein the first cup member portion
comprises an elastomer.
38. The device of claim 1, wherein the first cup member portion
comprises a rubber.
39. The device of claim 1, wherein the pressure control device
further comprises a second swellable element, the second swellable
element adapted, in use, to urge the second cup member portion
outwards into engagement with the surface.
40. The device of claim 39, wherein the second swellable element
swells at a slower rate than the first swellable element.
41. The device of claim 1, wherein the second cup member portion
comprises a swellable material.
42. The device of claim 1, wherein the second cup member portion
comprises an elastomer.
43. The device of claim 1, wherein the second cup member portion
comprises a rubber.
44. The device of claim 1, wherein the activation fluid is one of
water, oil and solvent.
45. The device of claim 1, wherein the first swellable element is
glued or bonded to the first cup member portion.
46. The device of claim 1, wherein the first swellable element is
separate from the first cup member portion.
47. The device of claim 1, wherein the at least one bypass is
parallel to the direction of fluid flow.
48. The device of claim 1, wherein the flexible cup member
comprises a back-up.
49. The device of claim 48, wherein the back-up is a garter
spring.
50. The device of claim 48, wherein the back up is one of: a
plurality of overlapping petals; a wire mesh; and a continuous
ductile ring.
51. The device of claim 1, wherein the support member is configured
to be sealed to a mandrel.
52. The device of claim 1, wherein the first portion of the cup
member defines a distal end of the cup member.
53. A method of isolating a section of a conduit, the method
comprising the steps of: positioning a pressure control device in a
conduit; activating a first swellable element under the action of
an activation fluid such that the first swellable element urges a
first portion of a control device flexible cup member outwards into
engagement with a surface of the conduit to form a lip seal with
said surface of the conduit; providing at least one bypass such
that the activation fluid can bypass the swellable element to build
up in a void behind a second portion of the cup member to move the
second portion of the cup member into engagement with the surface
of the conduit, wherein the walls of the at least one bypass are
stiffened by at least one stiffening device to prevent activation
of the swellable element by the portion of the activation fluid
while the portion of the activation fluid is in the at least one
bypass.
54. A system for isolating a section of a conduit, the system
comprising a plurality of pressure control devices, each device
comprising: a support member; a flexible cup member mounted to the
support member; a first swellable element, the first swellable
element adapted, upon activation by an activation fluid, to urge a
first portion of the cup member outwards into engagement with a
surface of the conduit; at least one bypass arranged to permit a
portion of activation fluid to bypass the swellable element to
permit build up in a void behind a second portion of the cup member
to move the second portion of the cup member into engagement with
the surface of the conduit; at least one stiffening device being
adapted to stiffen the walls of the at least one bypass and prevent
activation of the swellable element by the portion of the
activation fluid while the activation fluid is in the at least one
bypass.
55. The system of claim 54, wherein at least one of the cups faces
in a first direction and, at least one of the cups faces in a
second direction, the second direction being opposite the first
direction.
56. The system of claim 54, wherein there are a plurality of the
pressure control devices facing the same direction.
Description
FIELD OF THE INVENTION
The present invention relates to a pressure control device for
modulating pressure in a portion of a conduit.
BACKGROUND TO THE INVENTION
In the oil and gas exploration and extraction industries it is
often desirable to be able to modulate downhole pressure when
required. For example, it is desirable to isolate a section of well
bore to create sections of differential pressure within the bore. A
sealing device is used to create a seal within the bore, such that
fluid pressure on one side of the seal increases relative to fluid
pressure on the other side. Further, a temporary decrease in well
pressure can be used to initiate flow from the reservoir in a
process known as `swabbing`. One means of doing this is to make use
of a swab cup, which is a cup-shaped resilient member which is
lowered on a mandrel into the well. As a pressure differential
develops across the cup, the walls of the cup are pushed into
contact with the well tubing or bore wall, thereby sealing a
portion of the well. Thus, the pressure below the cup may decrease,
while the pressure above may increase.
Similarly-constructed pressure cups are also used in a wide variety
of other sealing and fluid lifting applications. For example,
variations in pressure may also be used to actuate or to control
other downhole tools and instruments which rely on fluid pressure
for their operation. Conventional cups are constructed with an
outer diameter slightly larger than that of the bore, such that a
seal is present even when the cup is not inflated.
Conventional pressure cups suffer from a number of disadvantages.
For example, as the cup is constructed with an outer diameter
slightly larger than the diameter of the bore, the cup will rub
against the bore as it is run into position. This can wear the cup
and may affect the formation of a seal between the cup and the bore
wall. Furthermore, if the bore has restrictions which narrow the
width of the bore, it may not be possible to pass the restriction
without damaging the pressure cup and an alternative sealing
mechanism is required.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is
provided a pressure control device for isolating a section of a
conduit, the device comprising:
a support member;
a flexible cup member mounted to the support member;
a first swellable element, the first swellable element adapted,
upon activation by an activation fluid, to urge a first portion of
the cup member outwards into engagement with a surface of the
conduit; and
at least one bypass arranged to permit the activation fluid to
bypass the swellable element and build up behind a second portion
of the cup member.
In an embodiment of the present invention, a pressure control
device is provided in which a flexible cup member is expanded
outwardly into contact with a conduit surface, such as a wellbore
surface or a downhole tubular surface under the action of a
swellable element. Once engaged with the surface, the fluid in the
conduit can not pass by the outer edge of the cup member and is
channelled, via the bypasses, to build up behind a second portion
of the cup member. Using a flexible cup member permits the cup
member to form an initial seal with conduits which are irregular
shapes such as open hole wellbore walls, and conduits which are,
for example, key seated.
In the preferred embodiment, the build up of fluid behind the
second cup member portion creates a pressure on the second cup
member portion.
The second cup member portion is adapted to be moved under the
action of the fluid pressure into engagement with the conduit
surface. In the preferred embodiment, the pressure is allowed to
build up sufficiently to move the second cup member portion into
engagement with the surface thereby increasing the seal with
between the cup member and the wellbore or tubular surface.
The pressure control device may define a throughbore.
The pressure control device may further comprise a mandrel, the
mandrel located in the device throughbore.
The first cup member portion is adapted to form a lip seal with the
surface.
The at least one bypass is defined by the first swellable
element.
Alternatively, the at least one bypass is defined by the first
swellable element and the mandrel.
Alternatively the at least one bypass is defined by the first
swellable element and the cup member first portion.
In one embodiment the pressure control device further comprises a
mandrel.
In this embodiment, the at least one bypass is defined by the
mandrel.
In one embodiment, a void is defined behind the second cup member
portion by the second cup member portion and the mandrel.
In one embodiment, a void is defined behind the second cup member
portion by the second cup member portion, the first swellable
element and the mandrel.
In an embodiment, the void comprises at least one inlet such that
fluid can flow into the void from the at least one bypass.
The support member is sealed to the mandrel. A seal is provided to
prevent the fluid leaving the void via the interface between the
support member and the mandrel.
The seal is located downstream of the void.
The seal is an o-ring seal.
The seal may hold pressure from one direction only.
The apparatus may further comprise at least one stiffening
device.
In one embodiment, the at least one stiffening device is adapted to
stiffen the walls of a bypass. If each bypass is completely or
partially defined by the swellable material and/or the cup member
first portion, there is a tendency for the bypass to close, either
partially or completely, as the swellable element swells and
pressure increases in the cup member. Stiffening devices are
provided to allow the bypass to continue to function as a
bypass.
The at least one stiffening device may define a bypass either
wholly or partially.
The at least one stiffening device may define a bypass in
combination with a mandrel.
The stiffening device is a length of tubular.
The at least one stiffening device may extend the full height of
the first swellable element.
The apparatus may comprise at least one anti-extrusion device. An
anti-extrusion device is provided to prevent the first swellable
element from swelling in an axial direction, thereby increasing the
swell in a radial direction towards the cup member first
portion.
In one embodiment there is a first anti-extrusion device preventing
swelling in a first axial direction.
In an alternative or additional embodiment there is a second
anti-extrusion device preventing swelling in a second axial
direction, opposite the first axial direction.
In this embodiment the anti-extrusion devices are connected.
The anti-extrusion devices are connected by a connecting
member.
The connecting member may wholly or partially define the at least
one bypass.
The connecting member may define the at least one bypass in
combination with a mandrel.
The anti-extrusion devices may define access means to permit the
fluid to access the first swellable element.
The anti-extrusion devices may be attached to a mandrel. Attaching
the anti-extrusion devices to a mandrel is preferred to attaching
them directly to the swellable element, as attaching the
anti-extrusion devices to the swellable element may inhibit
swelling of the element.
The anti-extrusion devices may be rings.
The connecting member is a tubular.
The first swellable element may comprise ethylene propylene rubber,
polyacrylic rubber, polyethers, acrylate polymers, tetra fluoro
ethylene-propylene and/or hydrogenated nitrile rubber or any
suitable compound.
The first swellable element may define the first cup member
portion.
Alternatively the first cup member portion may comprise a different
material.
In one embodiment the first cup member portion may comprise a
swellable material.
The first cup member portion may comprise an elastomer.
The first cup member portion may comprise a rubber.
The pressure control device may further comprise a second swellable
element, the second swellable element adapted, in use, to urge the
second cup member portion outwards into engagement with the
surface.
The second swellable element may swell at a slower rate than the
first swellable element. Such an arrangement permits the first
swellable element to swell the first cup member portion into
engagement with the surface and form a lip seal before the second
swellable element swells the second cup member portion into
engagement with the surface.
In one embodiment the second cup member portion may comprise a
swellable material.
The second cup member portion may comprise an elastomer.
The second cup member portion may comprise a rubber.
The activation fluid is water, oil or solvent or any suitable
fluid.
The first swellable element is glued or bonded to the first cup
member portion.
Alternatively, the first swellable element is separate from the
first cup member portion.
The/each bypass is parallel to the direction of fluid flow. Such an
arrangement minimises the length of flow path the fluid must travel
to reach the second cup member portion.
The flexible cup member may comprise a back-up. A back-up is
provided to prevent the cup member extruding down or along the
conduit under the action of the applied pressure.
In one embodiment the back-up could be a garter spring.
In an alternative embodiment the back up could be a plurality of
overlapping petals, a wire mesh, a continuous ductile ring, a
portion of harder material adapted to resist the pressure or any
suitable device or mechanism.
According to a second aspect of the present invention there is
provided a method of isolating a section of a conduit, the method
comprising the steps of:
positioning a pressure control device in a conduit;
activating a first swellable element under the action of an
activation fluid such that the first swellable element urges a
first portion of a control device flexible cup member outwards into
engagement with a surface of the conduit to form a lip seal with
said surface of the conduit;
providing a bypass such that the activation fluid can bypass the
swellable element to build up behind a second portion of the cup
member.
According to a third aspect of the present invention, there is
provided a system for isolating a section of a conduit, the system
comprising a plurality of pressure control devices, each device
comprising:
a support member;
a flexible cup member mounted to the support member;
a first swellable element, the first swellable element adapted,
upon activation by an activation fluid, to urge a first portion of
the cup member outwards into engagement with a surface of the
conduit; and
at least one bypass arranged to permit the activation fluid to
bypass the swellable element and build up behind a second portion
of the cup member.
In one embodiment at least one of the cups faces in a first
direction and, at least one of the cups faces in a second
direction, the second direction being opposite the first direction.
Such an arrangement permits pressure to be held from both ends or
sides of the system.
Alternatively or additionally, there are a plurality of the
pressure controlled devices facing the same direction. Such an
arrangement allows improved pressure containment and provides
redundancy in the system in the event that one of the cups fails or
leaks.
It will be understood that the features of one aspect of the
invention is equally applicable to other aspects and have not been
repeated for brevity.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be described with
reference to the accompanying drawings in which:
FIG. 1 is a section view of a pressure control device according to
a first embodiment of the present invention;
FIG. 2 is a section view of the pressure control device of FIG. 1
shown mounted on a mandrel;
FIG. 3 is a top view of the pressure control device of FIG. 1;
FIG. 4 is a section view of part of the pressure control device of
FIG. 1 shown in a run in configuration in a wellbore;
FIG. 5 is a section view of part of the pressure control device of
FIG. 1 shown in a partially set configuration in a wellbore;
FIG. 6 is a section view of part of the pressure control device of
FIG. 1 shown in a fully set configuration in a wellbore;
FIG. 7 is a section view of a pressure control device according to
a second embodiment of the present invention;
FIG. 8 is a section view of a pressure control device according to
a third embodiment of the present invention;
FIG. 9 is a section view of a pressure control device according to
a fourth embodiment of the present invention;
FIG. 10 is a section view of a pressure control device according to
fifth embodiment of the present invention; and
FIG. 11 is a section view of a pressure control device according to
a sixth embodiment of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
Reference is firstly made to FIGS. 1 and 2. FIG. 1 is a section
view of a pressure control device, generally indicated by reference
numeral 10, according to a first embodiment of the present
invention and FIG. 2 is a section view of the pressure control
device 10 of FIG. 1 shown fitted to a mandrel 12. The pressure
control device 10 is arranged to hold a pressure from above and
comprises a soft rubber flexible cup member 14, mounted and bonded
to a steel support member 16. The pressure control device 10
further comprises a first polyether swellable element 18, adapted,
in use, to urge a first portion 20 of the cup member 14, upon
activation, outwards (in the direction of arrows "A") into
engagement with a surface (not shown).
The pressure control device 10 further comprises four bypasses 22,
of which three 22a-c are shown on FIG. 1, arranged to permit a
fluid to bypass the swellable element 18 and build up in a void 46
behind a second portion 24 of the cup member 14. An o-ring seal 50
seals the interface between the support member 16 and the mandrel
12, preventing fluid leaking out of the void 46 (best seen in FIG.
2).
An anti-extrusion back-up 26 of nitrile rubber is also provided on
the cup member 14 to prevent the soft rubber flexible cup member 14
from extruding downwards when exposed to a pressure from above. The
anti-extrusion back-up 26 is biased to the position shown in FIGS.
1 and 2 by an annular spring 28. This will be discussed in greater
detail in due course.
Referring to FIG. 3, a plan view of the pressure control device 10
of FIG. 1, and to FIG. 2, each of the four bypasses 22 are defined
by the mandrel 12 and the first swellable element 18. The portion
of each bypass 22 defined by the swellable element 18 is lined by a
stiffening device 60, shown only in connection with the first
bypass 22a on FIG. 3. The stiffening devices 60 line the entire
surface of the bypasses 22 and are in contact with the mandrel 12
preventing extrusion of the swellable element 18 into the bypasses
22. The semi-circular section of the stiffening devices 60 helps
resist crushing by the swellable material.
The operation of the pressure control device 10 will now be
described with reference to FIGS. 4, 5 and 6, section views of part
of the pressure control device 10 of FIG. 1 in a run-in
configuration (FIG. 4), a partially set configuration (FIG. 5) and
a fully set configuration (FIG. 6).
In FIG. 4 the pressure control device 10 has been run into a
wellbore 40 defining a wellbore surface 42. Water (W) is pumped
down the wellbore 40 and comes into contact with the pressure
control device 10. As can be seen, the water flows down the
bypasses 22 into the void 46 between the cup member second portion
24 and the mandrel 12, and down an annulus 44 between the pressure
controlled device 10 and the wellbore surface 42.
The swellable material in the first swellable element 18 is
activated by contact with water and, referring to FIG. 5, the water
causes the swellable element 18 to swell up, pushing the first cup
member portion 20 into contact with, and form a lip seal with, the
wellbore surface 42.
Once the cup member 14 has formed a lip seal with the wellbore
surface 42, the fluid path down the annulus 44 is closed and
pressure builds up in the void 46 beneath the swellable element 18.
The pressure is held by the o-ring seal 50 which prevents leakage
between the steel support member 16 and the mandrel 12.
Pressure begins to build up in the void 46, forcing the cup member
second portion 24 into engagement with the wellbore surface 42. The
anti-extrusion back-ups 26 and the annular spring 28 also rotate
outwards against the bias of the annular spring 28 preventing
extrusion of the flexible cup member 14 down the annulus 44, and
maintaining the integrity of the cup member 14. Continued
application of pressure on the pressure control device 10 from
above will maintain the seal and energise the pressure control
device 10 to hold the pressure.
Referring now to FIG. 7, a pressure control device 110 is shown in
accordance with the second embodiment of the present invention.
This pressure control device 110 is similar in most respects to the
pressure control device 10 of the first embodiment, however the
pressure control device 110 of the second embodiment includes an
anti-extrusion ring 170 mounted to an upper surface of the
swellable element 118 to prevent the swellable element 118 from
swelling in an upward (axial) direction, therefore increasing the
swell in the radial direction.
A first portion 180 of the anti extrusion device 170 is glued or
otherwise bonded to an upper surface 172 of the swellable element
118 and a second portion 182 is glued or otherwise bonded and
sandwiched between the cup member first portion 120 and the
swellable material 118. The device upper portion 180 defines a
plurality of holes (not visible) to permit the swelling fluid to
contact the upper surface of the swellable element 118. It is
believed that the upper surface of the swellable element, is where
the most swelling occurs.
FIG. 8 shows a pressure control device 210 according to a third
embodiment of the present invention. In this embodiment, the
bypasses 222 are wholly defined by the swellable element 218. In
the embodiment shown in FIG. 8, the bypasses 222 are circular in
cross section and moulded into the swellable element 218 during
manufacture.
FIG. 9 shows a fourth embodiment of the present invention. In this
embodiment, the pressure control device 310 includes a swellable
element 318 which also defines the cup member first portion 320. In
essence the cup member first portion 320 is moulded from a
swellable material. In addition the second portion 324 of the
flexible cup member 314 is also moulded from a swellable material.
In this embodiment, the second portion swellable material 324
swells at a slower rate than the first portion swellable material
318 and is believed the use of a swellable material in this way can
improve the seal.
FIG. 10 shows a pressure control device 410 according to a fifth
embodiment of the present invention. In this embodiment, there are
upper and lower anti-extrusion devices in the from of rings 470a,
470b. These anti-extrusion rings 470 are attached to the mandrel
412 rather than the swellable element 418 so that swelling of the
element 418 is not inhibited in the radial direction by bonding
between the rings 470 and the swellable element 418.
FIG. 11 shows a pressure control device 510 according to a sixth
embodiment of the present invention. In this embodiment, rather
than being attached to a mandrel, the upper and lower
anti-extrusion rings 570a, 570b are attached to a tubular
connecting member 590. The connecting member 590 permits
positioning of the anti-extrusion rings 570 above and below the
swellable element 518 without the need to bond the anti-extrusion
rings 570 to the swellable element 518. The combination of the
anti-extrusion rings 570 and the connecting member 590 prevents the
swellable element 518 swelling in any direction other than radially
outwardly, towards the cup member first portion 520, thereby
maximising the effect of the swellable element 518.
The connecting member 590 partially defines the bypasses 522, the
bypasses 522 being wholly defined by the connecting member 590 and
a mandrel (not shown).
In the embodiments of FIGS. 10 and 11, the anti-extrusion devices
470, 570 and where applicable the connecting member 590 define
apertures to allow the fluid to access the swellable element
418,518 to swell the element 418,518.
Various modifications and improvements can be made to the above
described embodiment without departing from the scope of the
present invention. For example, although the bypasses are shown as
being defined by the swellable element alone or the swellable
element in conjunction with a mandrel, they could be defined by the
swellable element in conjunction with the flexible cup member.
Additionally it will be understood that although the pressure
control device is shown holding pressure from above, it will be
understood that the control device could be inverted to hold
pressure from below, or the device could be one of a plurality of
devices, arranged in series, to hold pressure from one direction or
facing in opposite directions to hold pressure from above and
below.
Furthermore it will also be understood that although a hard rubber
back-up is used in the embodiments described, an overlapping petal
arrangement of back-up could also be used.
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